make vmstat cpu-unplug safe

[KOSAKI Motohiro]

btw: I think all_vm_event() author is Cristoph Lameter, right?


--------------------------------------------
When access cpu_online_map, We should prevent that dynamically 
change cpu_online_map by get_online_cpus().

Unfortunately, all_vm_events() doesn't it.

Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
CC: Christoph Lameter <clameter@xxxxxxx>

---
 mm/vmstat.c |    2 ++
 1 file changed, 2 insertions(+)

Index: b/mm/vmstat.c
===================================================================
--- a/mm/vmstat.c       2008-05-04 23:00:52.000000000 +0900
+++ b/mm/vmstat.c       2008-05-06 16:13:32.000000000 +0900
@@ -42,7 +42,9 @@ static void sum_vm_events(unsigned long
 */
 void all_vm_events(unsigned long *ret)
 {
+       get_online_cpus();
        sum_vm_events(ret, &cpu_online_map);
+       put_online_cpus();
 }
 EXPORT_SYMBOL_GPL(all_vm_events);



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